Known in the art is a process for recuperation of organic solvents in dry-cleaning machines comprising circulation of air by means of a blower through a cleaning drum of a machine, containing articles treated with an organic solvent and squeezed, a filter, an air-cooler and a heater. The circulated air is heated in the heater, the organic solvent is recovered from the above-mentioned articles as a vapour by means of the circulated air, the heated circulated air containing vapours of the organic solvent is cleaned in a filter to remove mechanical foreign matter; the cleaned heated circulated air containing vapours of the organic solvent is cooled in an air cooler with condensation of vapours of the organic solvent. On completion of the formation of a condensate of the vapours of the organic solvent air is circulated by means of the above-mentioned blower through the above-mentioned cleaning drum, filter and air cooler, as well as an evaporator of the cooling machine. The circulated air is used to recover the organic solvent as a vapour from the treated articles; the circulated air containing vapours of the organic solvent is cleaned in a filter to remove mechanical foreign matter; the cleaned circulated air containing vapours of the organic solvent is cooled first in the air cooler and then in the cooling machine evaporator. The cooling surface of the evaporator has temperature of about -20.degree. C. Owing to cooling of air in the cooling machine evaporator the organic solvent is condensed (U.S. Pat. No. 3,807,948).
A disadvantage of this prior art process for recuperation of organic solvents resides in an incomplete recovery thereof from the circulated air in the cooling machine evaporator. Thus, upon cooling of circulating air containing an organic solvent to a temperature of about -15.degree. C. 17 g of perchlorethylene or 70 g of trichlorethylene remain in 1 m.sup.3 of the air. This results, in turn, in losses of organic solvents which penetrate into the atmosphere upon discharging of treated articles from the cleaning drum and thus causes pollution of the environment.
Another disadvantage of this prior art process resides in high rates of electric power consumption in the case of using a cooling machine for condensation of an organic solvent from the circulated air.
Still another disadvantage of this process is a relatively low speed of condensation of the organic solvent in an evaporator of the cooling machine, this factor extending the recuperation process and lowering productivity of dry-cleaning machine.
A further disadvantage of this prior art process resides in that upon air circulation through the cleaning drum and cooling machine evaporator no natural wetness of the treated articles is retained due to recovery of not only the organic solvent from the treated articles but of water contained therein as well. There occurs over-drying of the articles, wherefore the quality of their cleaning is impaired. To restore the natural wetness of the articles, it is necessary to supply a corresponding amount of steam or atomized water into the cleaning drum, wherefore the operation of a dry-cleaning machine is made more complicated.
A still further disadvantage of the above-discussed process resides also in the necessity of using sophisticated and expensive cooling machinery for the maintenance of which a skillful operating personnel is required.
Also known in the art is a process for recuperation of organic solvents in dry-cleaning machines, comprising circulation of air by means of a blower through a cleaning drum of the machine, containing textile articles treated with an organic solvent and squeezed, a filter, an air cooler and a heater. The circulated air is heated in a heater, the organic solvent is recovered from said articles as a vapour by means of the heated circulated air; the heated circulated air containing vapours of the organic solvent is cleaned in a filter to remove mechanical foreign matter; the cleaned heated circulated air containing vapours of the organic solvent is cooled in an air cooler with condensation of the vapours of the organic solvent. On completion of the formation of a condensate of the vapours of the organic solvent air is circulated by means of the above-mentioned blower through said cleaning drum, filter and air-cooler, as well as an adsorber. The organic solvent is recovered from said articles as a vapour by means of the circulated air, the circulated air containing vapours of the organic solvent is cleaned in a filter from mechanical foreign matter, the cleaned circulated air containing vapours of the organic solvent is cooled in the air cooler and the organic solvent is adsorbed from the cooled cleaned circulated air in the adsorber. After several (about 20-30) process cycles of operation of the dry-cleaning machine (the term process cycle of the machine operation means operation of the machine from the moment of loading of dirty textile articles into the cleaning drum of the machine till the moment of discharging clean articles from the drum), each of them comprising circulation of air first through the cleaning drum, filter, air cooler and heater and then through the cleaning drum, filter, air cooler and adsorber, the adsorbed organic solvent is desorbed from the adsorbent by passing steam therethrough under a pressure of from 0.3 to 0.7 MPa. The steam passed through the adsorbent and vapours of the desorbed organic solvent are condensed in a condenser with water cooling to give a mixture of condensates which is cooled in the same condenser, whereafter the cooled mixture is separated into the organic solvent and water. On completion of desorption of the organic solvent steam is stopped to be passed through the adsorbent, and the steam and its condensate remaining after desorption are removed from the adsorber by means of heated air into the atmosphere (i.e. drying of the adsorbent is thus effected).
The desorption of the organic solvent from the adsorbent, condensation of the steam passed through the adsorbent and of vapours of the desorbed organic solvent, cooling of the resulting mixture of condensates, separation of the cooled mixture of condensates into the organic solvent and water and purging of heated air through the adsorber are effected for one hour while stopping air circulation (cf. Express information, CBSTI/Central Bureau of Scientific and Technological Information/, RSFSR Ministry of Household Servicing of Polulation, Series IV, Issue 3, 1980, June, Moscow; A. M. Epifanov, M. A. Kochetkov "Specific Features of the Design and Operation of the Dry-Cleaning Machine "Spetsima-212", pp. 14-19).
In this prior art process during the first several process cycles there occurs a substantially complete adsorption of the organic solvent from the circulated air. However, in the subsequent process cycles the degree of catching of organic solvents from the circulated air gradually diminishes due to saturation of the adsorbent with the organic solvent. This results in an increased amount of organic solvents remaining in the cleaning drum and in the articles contained therein and, hence, in increased losses of them and pollution of the environment. Furthermore, losses of the organic solvents and pollution of the environment therewith can occur during purging of the heated air through the adsorber for the removal of the steam and its condensate remaining therein, since a portion of the undesorbed organic solvent may be vented to the atmosphere together with the purging air.
Since after drying of the adsorbent a small amount of the steam condensate remains therein, in carrying out first process cycles upon air circulation through the adsorbent this condensate passes in atomized state into the cleaning drum, whereby natural wetness of the articles remaining in the cleaning drum is restored. Nevertheless, as the amount of the steam condensate in the adsorber gets lower in carrying out further process cycles of the machine operation, the admission of the steam condensate into the cleaning drum stops, whereby overdrying of articles takes place and, hence, their quality is impaired. It is, however, inadmissible to leave a high quantity of the steam condensate in the adsorbent after its drying, since this condensate passes into the cleaning drum in a non-atomized state in a great amount which may cause shrinkage of the articles.
Compared to the previously discussed prior art process, this process rules out the necessity of power consumption for condensation of organic solvents from the circulated air.
However, for carrying out of that process a considerable rate of steam consumption is necessary for heating the circulated air in the heater, desorption of the organic solvent and heating of the air used to remove the steam and its condensate remaining after desorption of the organic solvent from the adsorber, as well as a high rate of consumption of cooling water for condensation of the steam passed through the adsorbent and vapours of the desorbed organic solvent.
This process has another disadvantage residing in that upon admission of the steam supplied into the adsorber for description of the organic solvent a sharp reduction of the steam pressure occurs, which results in a lowering of its temperature and, hence, in a lesser efficiency of the desorption process.
This prior art process makes it possible to reduce duration of recuperation of organic solvents as compared to that discussed hereinbefore. However, for its carrying out additional time is required for desorption of the organic solvent from the adsorbent, condensation of the steam passed through the adsorbent and of vapours of the desorbed organic solvent, cooling of the resulting mixture of condensates, separation thereof into the organic solvent and water and the removal of the steam and its condensate remaining in the adsorber after the desorption of the organic solvent (drying of the adsorbent), since in performing these operations the air circulation is stopped, i.e. the operation of the dry-cleaning machine is discontinued. Such periodic shutdowns result in a lowered productivity of the machine.
This process does not require, as compared to the previously discussed one, qualified operating personnel for the maintenance of the coiling machinery; however, in this process maintenance of the dry-cleaning machine is more complicated owing to the necessity of periodic shutdowns of the machine for carrying out the above-mentioned operations.
In the case of using two alternatingly operating adsorbers the design of the dry-cleaning machine is substantially complicated, while its maintenance is not simplified.
Also known in the art is a process for removing steam, its condensate and the organic solvent remaining after the desorption of the organic solvent during its recuperation from the adsorber, wherein the steam, its condensate and a portion of the non-desorbed organic solvent in the vaporous state are removed by means of heated air into a water-cooled condenser, followed by cooling of the resulting mixture of the condensates and its separation into water and the organic solvent (U.S. Pat. No. 4,440,549).
This prior art process has a disadvantage residing in the necessity of consumption of cooling water for condensation of steam and vapours of the non-desorbed organic solvent, as well as in losses of heat evolved in this condensation.